Spring快速入门

Spring的快速入门

1、什么是Spring？

Spring实质上就是一个容器，用来管理bean(对象)，这些bean包括service层、dao层里面的所有对象、Mybatis的SqlSessionFactoryBean对象以及数据源连接池对象，这些都归Spring来进行管理

2、快速搭建一个简单案例，帮助大家理解Spring

一、 在pom.xml文件中导入相关的依赖

<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0"
         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0</modelVersion>

    <groupId>cn.zyyx</groupId>
    <artifactId>springdemo</artifactId>
    <version>1.0-SNAPSHOT</version>

    <!-- 依赖的管理 -->
    <dependencies>
        <!-- 单元测试Junit -->
        <dependency>
            <groupId>junit</groupId>
            <artifactId>junit</artifactId>
            <version>4.11</version>
        </dependency>
        <!-- Mysql的连接依赖 -->
        <dependency>
            <groupId>mysql</groupId>
            <artifactId>mysql-connector-java</artifactId>
            <version>5.1.39</version>
        </dependency>
        <!-- 引入druid连接池 -->
        <dependency>
            <groupId>com.alibaba</groupId>
            <artifactId>druid</artifactId>
            <version>1.0.19</version>
        </dependency>
        <!-- 导入spring的context-support依赖，会自动引入spring的其它依赖 -->
        <dependency>
            <groupId>org.springframework</groupId>
            <artifactId>spring-context-support</artifactId>
            <version>4.3.3.RELEASE</version>
        </dependency>
        <!-- 引入spring-jdbc的依赖 -->
        <dependency>
            <groupId>org.springframework</groupId>
            <artifactId>spring-jdbc</artifactId>
            <version>4.3.3.RELEASE</version>
        </dependency>
    </dependencies>
</project>

二、 创建实体类Users、UserDao、UserService等类

1、实体类User

package cn.zyyx.domain;

public class User {
    private Integer id;
    private String name;
    private Integer age;

    public Integer getId() {
        return id;
    }

    public void setId(Integer id) {
        this.id = id;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public Integer getAge() {
        return age;
    }

    public void setAge(Integer age) {
        this.age = age;
    }

    @Override
    public String toString() {
        return "User{" +
                "id=" + id +
                ", name='" + name + '\'' +
                ", age=" + age +
                '}';
    }
}

2、Dao层的BaseDao和UserDaoImpl

package cn.zyyx.dao;
import java.util.List;
public interface BaseDao<T> {
    void insert(T t);
    void delete(Integer id);
    void update(T t);
    T selectOne(Integer id);
    List<T> selectAll();
}

package cn.zyyx.dao.impl;
import cn.zyyx.dao.BaseDao;
import cn.zyyx.domain.User;
import cn.zyyx.util.Util;
import org.springframework.context.ApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;
import javax.sql.DataSource;
import java.sql.*;
import java.util.ArrayList;
import java.util.List;

public class UserDaoImpl implements BaseDao<User> {
    /*
        增加
     */
    public void insert(User user) {
        Connection connection = Util.getConnection();
        String sql = "insert into users(name,age) values(?,?)";
        PreparedStatement ps = null;
        try {
           ps = connection.prepareStatement(sql);
           ps.setString(1,user.getName());
           ps.setInt(2,user.getAge());
           ps.execute();
           ps.close();
           connection.close();
        } catch (SQLException e) {
            e.printStackTrace();
        }
    }
    /*
        删除
     */
    public void delete(Integer id) {
        Connection connection = Util.getConnection();
        String sql = "delete from users where id = ?";
        PreparedStatement ps = null;
        try {
            ps = connection.prepareStatement(sql);
            ps.setInt(1,id);
            ps.execute();
            ps.close();
            connection.close();
        } catch (SQLException e) {
            e.printStackTrace();
        }
    }

    public void update(User user) {
        Connection connection = Util.getConnection();
        String sql = "update users set name = ? , age = ? wherre id = ?";
        PreparedStatement ps = null;
        try {
            ps = connection.prepareStatement(sql);
            ps.setString(1,user.getName());
            ps.setInt(2,user.getAge());
            ps.setInt(3,user.getId());
            ps.executeUpdate();
            ps.close();
            connection.close();
        } catch (SQLException e) {
            e.printStackTrace();
        }
    }

    public User selectOne(Integer id) {
        Connection connection = Util.getConnection();
        String sql = "select * from users where id = ?";
        PreparedStatement ps = null;
        User user = null;
        try {
            ps = connection.prepareStatement(sql);
            ps.setInt(1,id);
            ResultSet resultSet = ps.executeQuery();
            while (resultSet.next()){
                user = new User();
                user.setId(resultSet.getInt("id"));
                user.setName(resultSet.getString("name"));
                user.setAge(resultSet.getInt("age"));
            }
            ps.close();
            connection.close();
        } catch (SQLException e) {
            e.printStackTrace();
        }
        return user;
    }

    public List<User> selectAll() {
        Connection connection = Util.getConnection();
        String sql = "select * from users";
        PreparedStatement ps = null;
        List<User> userList = new ArrayList<User>();
        try {
            ps = connection.prepareStatement(sql);
            ResultSet resultSet = ps.executeQuery();
            while (resultSet.next()){
                User user = new User();
                user.setId(resultSet.getInt("id"));
                user.setName(resultSet.getString("name"));
                user.setAge(resultSet.getInt("age"));
                userList.add(user);
            }
            ps.close();
            connection.close();
        } catch (SQLException e) {
            e.printStackTrace();
        }
        return userList;
    }
}

3、Service层的UserService类

package cn.zyyx.service;

import cn.zyyx.dao.BaseDao;
import cn.zyyx.domain.User;

public class UserService {

    private BaseDao<User> userDao;

    public void setUserDao(BaseDao<User> userDao) {
        this.userDao = userDao;
    }

    public BaseDao<User> getUserDao(){
        return userDao;
    }
}

4、工具类Util

package cn.zyyx.util;

import java.sql.Connection;
import java.sql.SQLException;

import org.springframework.context.ApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;

import javax.sql.DataSource;

public class Util {
    public static Connection getConnection() {
        ApplicationContext ac = new ClassPathXmlApplicationContext("beans.xml");
        DataSource dataSource = (DataSource) ac.getBean("dataSource");
        Connection connection = null;
        try {
            connection = dataSource.getConnection();
        } catch (SQLException e) {
            e.printStackTrace();
        }
        return connection;
    }
}

三、 在resources资源文件夹下创建Spring的核心配置文件beans.xml，并进行如下配置

<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
       xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
       xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd">

       <!-- 配置Druid连接池 -->
        <bean id="dataSource" class="com.alibaba.druid.pool.DruidDataSource">
            <!-- 驱动 -->
            <property name="driverClassName" value="com.mysql.jdbc.Driver"/>
            <!-- url -->
            <property name="url" value="jdbc:mysql://localhost:3306/mybatis"/>
            <!-- 用户名 -->
            <property name="username" value="root"/>
            <!-- 密码 --。
            <property name="password" value="root"/>
            <!-- 最大连接数 -->
            <property name="maxActive" value="10"/>
            <!-- 最小连接数 -->
            <property name="minIdle" value="2"/>
            <!-- 初始化连接数 -->
            <property name="initialSize" value="3"/>
        </bean>
        <!-- 对dao层的bean进行管理 -->
        <bean id="userDao" class="cn.zyyx.dao.impl.UserDaoImpl"/>
        <!-- 对service层的bean进行管理 -->
        <bean id="userService" class="cn.zyyx.service.UserService">
            <!-- 将userDao注入到userSerice里面 -->
            <property name="userDao" ref="userDao"/>
        </bean>
</beans>

四、 创建一个测试类进行单元测试

package cn.zyyx.test;

import cn.zyyx.dao.BaseDao;
import cn.zyyx.domain.User;
import cn.zyyx.service.UserService;
import org.junit.Test;
import org.springframework.context.ApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;

public class TestSpring {
    @Test
    public void testSpring(){
    	 //获得Spring容器
        ApplicationContext ac = new ClassPathXmlApplicationContext("beans.xml");
        //获取UserService对象
        UserService userService = (UserService) ac.getBean("userService");
        //调用方法获取UserDao
        BaseDao<User> userDao = userService.getUserDao();
        //执行查询语句并且返回结果
        System.out.println(userDao.selectOne(9));
    }
}

测试结果为

我的users表

五、 总结
Spring的本质就是对很多bean(即对象)进行管理，从beans.xml文件(可以看作为Spring容器)中，我们明显看出，Spring管理了数据源、UserDaoImpl以及UserService三个bean，这就是控制反转(IOC)，并且将UserDaoImpl的bean赋给UserSerivce的属性，同时体现了依赖注入DI。从另一个角度来讲，IOC和DI本质上时同一个概念，只不过是从不同的角度来描述问题罢了。本人水平有限，希望能够帮助初学者了解到Spring的核心思想。
六、 代码
链接：https://pan.baidu.com/s/1axAFq6wyU6YYJJ0dPhxJPA
提取码：dzq5